Liquid-phase deposition of thin films onto the surface of battery electrodes

ABSTRACT

Methods, systems, and compositions for the liquid-phase deposition (LPD) of thin films. The thin films can be coated onto the surface of porous components of electrochemical devices, such as battery electrodes. Embodiments of the present disclosure achieve a faster, safer, and more cost-effective means for forming uniform, conformal layers on non-planar microstructures than known methods. In one aspect, the methods and systems involve exposing the component to be coated to different liquid reagents in sequential processing steps, with optional intervening rinsing and drying steps. Processing may occur in a single reaction chamber or multiple reaction chambers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/244,024, filed Jan. 9, 2019, now issued as U.S. Pat. No. 10,985,360,which application is a continuation of International Application No.PCT/US2018/038612, filed Jun. 20, 2018, which claims priority to U.S.Provisional Application No. 62/522,470, filed on Jun. 20, 2017, thesubject matter of all of which are hereby incorporated by reference asif fully set forth herein.

BACKGROUND

Traditional vapor phase atomic layer deposition (ALD) techniques rely onthe evaporation of metal organic precursors in an evacuated chamber.Substrates placed within this chamber are exposed to the impinging fluxof metalorganic vapor. Substrate surfaces, which are oftenhydroxyl-terminated, react with impinging vapor to produce precisely oneself-limiting, surface-saturating monolayer of adsorbed metal organic.In one Instance, metal organic adsorption, followed by purge of excessmetal organic using vacuum and inert gas, followed by exposure ofsubstrate surface to an oxidizer (such as H₂O, O₂ or O₃) results in theformation of precisely one monolayer of metal oxide.

ALD is particularly well-suited for generating conformal coatings withprecise thicknesses on substrates possessing a porous microstructure.One example of such a substrate is a lithium-ion battery (LIB)electrode. State-of-the-art LIB electrodes are typically fabricated bycoating slurries of anode or cathode particles mixed with binder andconductive additive onto foil current collectors. The open spaceremaining between particles after coating generates porosity throughoutthe thickness of electrode films. Substrates possessing this kind ofmorphology often cannot be adequately coated by other physical vapordeposition (PVD) processes (such as sputtering) because of“line-of-sight” limitations. Typically, deposition cycles in suchtechniques allow for little surface mobility of adsorbed atoms beforereaction to complete product. As a result, only regions of substratethat are directly exposed to impinging flux of atoms are adequatelycoated. To conformally and uniformly coat all surfaces within a porousmorphology, a deposition technique akin to ALD is required, wheresubstantial time is allowed for surface mobility of adsorbed atoms priorto reaction. ALD coatings on lithium-ion battery electrodes have beendemonstrated to reduce deleterious side reactions typically associatedwith capacity fade such as solid-electrolyte-interphase (SEI) formation.However, numerous manufacturing limitations of traditional ALD processespresent a need for a more manufacturable process that achieves similarfilm quality, uniformity and conformality.

While metal organic reagents (i.e., precursors) used in ALD of oxidessuch as Al₂O₃ and ZnO (trimethylaluminum (TMA) and diethylzine (DEZ),respectively) evaporate at relatively low temperatures (<100° C.) and atmodest base vacuum pressures (>1 Torr), most metalorganic precursorsrequire temperatures greater than 100° C. (and many greater than 200°C.) to yield a substantial vapor pressure. The key drawback to highprecursor boiling point is that the substrate temperature must also bemaintained above the precursor boiling point to prevent condensation ofprecursor on substrate surfaces. Precursor condensation results in lossof monolayer-by-monolayer growth control, which in turn, results inunpredictable final film thickness. Substrates in an evacuated ALDchamber also often need to be heated radiatively (as with suspendedroll-to-roll foil substrates), due to the lack of a heat transfermedium. Radiative heating is inefficient for reflective foil substratessuch as those used in battery electrodes. High substrate temperatures(>200° C.) are also impractical for battery electrodes because polymerbinders (such as PVDF) used in electrode coating degrade at suchtemperatures. Residual gases trapped within layers of roll-to-rollsubstrates also lengthen pump down time in traditional ALD chambers, andthe loss of unused precursor through continuous purge and evacuationresult in poor materials utilization in traditional ALD processes. Thepyrophoric nature of the gaseous metalorganic precursors typically usedin traditional ALD processes also requires the incorporation of costlysafety infrastructure.

In U.S. PGPUB 2016/0351973, vapor phase ALD and derivative depositiontechnologies were disclosed to reduce SEI formation by directly coatingbattery electrode constituent powders with various encapsulatingcoatings prior to slurry formation. Such a technology avoids certainlimitations of ALD coating of formed electrodes such as substratetemperature. However, a key shortcoming of this technology is that, thepassivating layers formed in this manner introduce substantial electrodeinternal resistance. Internal resistance can greatly limit battery poweroutput due to voltage drop. In order for an encapsulating, passivatinglayer to function well as an inhibitor to deleterious side reactions, itmust inhibit electron transfer between electrode and electrolyte. Wideband-gap insulating materials, as indicated in the '973 application, aregood candidates for such an application. Unfortunately, when applied toindividual electrode powder particles, they will also impedeparticle-to-particle electron transfer, which will result in internalresistance. The only way to circumvent the issue of internal resistancewhile maintaining the benefit of a passivating layer between electrodeand electrolyte is to deposit the passivating layer on a pre-formedbattery electrode.

High quality, conformal thin films of oxides and chalcogenides have beendeposited for decades by techniques other than ALD, such as chemicalbath deposition (CBD), successive-ionic layer adsorption and reaction(SILAR) and layer-by-layer sol-gel. In the CBD technique, (typically)aqueous solutions of complexed metal precursors are mixed withchalcogenide or oxide ion sources. Temperatures for these processes areusually modest, well below decomposition temperatures for batteryelectrode materials, binders or separators. CBD is best known for beingused for depositing high quality CdS or ZnS as the n-type junctionpartner on CdTe or CIGS thin film solar cells. This technique has beenused for years to set world record efficiencies for these types of solarcells. They have yielded high open-circuit voltages, high diode idealityand high shunt resistance, indicating excellent film quality andconformality. CBD processes have also been commercialized intohigh-volume thin film solar cell production lines.

A useful variation of the CBD technique is SILAR. In this instance,substrates are alternately exposed to cationic and anionic reactantsolutions, with rinse steps in between. While this technique results inslower film growth, a benefit of the technique is the elimination ofhomogenous nucleation (precipitation) from intermixing of the tworeactants, which dramatically improves materials utilization.Considering the fact that the tunneling limit of a good dielectric is onthe order of 1-2 nm, SILAR techniques are feasible for deposition ofpassivation layers on battery electrode surfaces. Thickness control inSILAR processes is also better than in CBD processes; thickness controlof a passivation layer on battery electrodes, for instance, is criticalto prevent unwanted barriers to lithium diffusion while maintaining anelectron tunneling barrier.

Solution-based techniques also exist that demonstrate layer by layersol-gel coating using the same kinds of metal organics used in vaporphase ALD. For instance, an Al₂O₃ monolayer can be grown by immersion ofa substrate in a solution of an appropriate aluminum alkoxide. Theadsorption of the metalorganic precursor, followed by an oxidizing stepsuch as hydrolysis, can yield one monolayer of oxide. These steps arerepeated with rinse steps in between to yield monolayer-by-monolayercoatings. The metal alkoxide precursors are typically soluble to veryhigh molarities in standard organic solvents like 2-propanol. In recentyears, high quality Al₂O₃. SiO₂ and ZrO₂ recombination blocking layerswere all grown on TiO₂ dye-sensitized solar cells using this technique.

U.S. PGPUB 2016/0090652 presents a liquid phase ALD method akin to thatdescribed above, wherein discrete wafer substrates are consecutivelyexposed to a solution of metalorganic precursor, a rinse solvent toremove excess metalorganic, an oxidizing solution and another rinse.These four steps are repeated to yield any desired thickness of film.The wafer is attached to a spin-coating apparatus; immediately aftereach step the wafer is spun to remove excess fluid. While this techniquemay work well for substrates similar to wafers, the process cannot beused to coat continuous substrates such as rolls of foil.

Therefore, a need exists for an alternative deposition method to ALD andother conventional methods that is faster, more efficient, safer, andmore cost-effective for yielding conformal coatings on the surface ofbattery electrodes. To-date, solution deposition equipment that depositsconformally grown thin films on rolls of battery electrodes atcommercial scale has not yet been demonstrated. Examples of keydifficulties that have yet to be solved include homogeneous nucleationduring film growth, cross-contamination of precursor solutions anduniformity of film thickness at all locations in the film

SUMMARY

The present disclosure provides liquid-phase deposition methods,systems, and compositions for generating a thin-film coating. The thinfilms described herein are particularly useful for coating the surfacesof porous components used in electrochemical devices, such as batteryelectrodes or battery separator membranes. The methods and systems ofthe present disclosure promote precise control of thickness andconformality of desired films by allowing reagents to adsorb and moveacross substrate surfaces as in ALD, albeit through a liquid-phasedelivery instead of vapor-phase. Liquid-phase delivery of reagents takesadvantage of the energy of solvation to mobilize reagents instead ofrelying on high-temperature thermal evaporation.

In certain aspects, the present disclosure relates to a method forcoating a thin film onto a surface of a battery electrode, comprising

-   -   (a) providing a battery electrode onto a conveyance apparatus;    -   (b) transferring, by the conveyance apparatus, the battery        electrode to a first reaction chamber comprising at least a        first liquid solution comprising a first reagent;    -   (c) exposing, by the conveyance apparatus, the battery electrode        to the first liquid solution to produce a partially coated        battery electrode having a layer comprising an adsorbed first        reagent on the surface of the battery electrode,    -   (d) transferring, by the conveyance apparatus, the partially        coated battery electrode to a second reaction chamber comprising        a second liquid solution comprising at least a second reagent,        and    -   (e) exposing, by the conveyance apparatus, the partially coated        battery electrode to the second liquid solution, wherein the at        least second reagent reacts with the first adsorbed reagent of        the partially coated battery electrode to produce a fully coated        battery electrode comprising a monolayer of thin film coated        onto the surface of the fully coated battery electrode, the        monolayer of thin film comprising a compound generated from the        reaction of the second reagent and the absorbed first reagent.

In certain embodiments, the monolayer of thin film has a thickness fromabout 0.5 nm to 100 μm. In some embodiments, the monolayer of thin filmmay be composed of grains having a size 0.5 nm to 100 μm. In otherembodiments, the monolayer of thin film may be crystalline or amorphous.

In certain embodiments, the battery electrode has a thickness of 100 nmto 1,000 μm. In other embodiments, the battery electrode to be coatedhas pores ranging in size of 0.1 nm to 100 μm. In some embodiments, thebattery electrode to be coated has a film porosity of 1-99%. In someembodiments, the battery electrode is composed of graphite. Si, Sn, aSi-graphite composite, a Sn-graphite or lithium metal. In otherembodiments, the battery electrode is composed ofLiNi_(x)Mn_(y)Co_(z)O₂, LiNi_(x)Co_(y)AlO₂, LiMn_(x)Ni_(y)O_(z), LiMnO₂,LiFePO₄, LiMnPO₄, LiNiPO₄, LiCoPO₄, LiV₂O₅, sulfur or LiCoO₂ where x, yand z are stoichiometric coefficients.

In certain embodiments, the conveyance apparatus may be a roll-to-rolldeposition system. In some embodiments, the conveyance apparatuscomprises a series of rollers for guiding the battery electrode andpartially coated battery electrode to the first and second reactionchambers, respectively.

In certain embodiments, the battery electrode is exposed, eitherpartially or fully, to the first liquid solution by a process selectedfrom the group consisting of submerging, spraying, slot die coating, andgravure roller coating. In other embodiments, the partially coatedbattery electrode is exposed, either partially or fully, to the secondliquid solution by a process selected from the group consisting ofsubmerging, spraying, slot die coating, and gravure roller coating. Insome embodiment, the first and second liquid solutions are non-ionic.

In certain embodiments, the method further comprises rinsing thepartially coated battery electrode with a first rinsing solutioncomprising a first solvent to produce a saturated first layer on thepartially coated battery electrode and a first residual solutioncomprising the first solvent and unreacted first reagent. In someembodiments, the method further comprises passing the first residualsolution to a first filtration step to separate unreacted first reagentfrom the first solvent.

In certain embodiments, the method further comprises rinsing the fullycoated battery electrode with a second rinsing solution comprising asecond solvent to produce a saturated monolayer of thin film on thefully coated battery electrode and a second residual solution comprisingthe second solvent and unreacted second reagent. In some embodiments,the method further comprises passing the second residual rinsingsolution to a second filtration step to separate the unreacted secondreagent from the second solvent. In other embodiments, the methodfurther comprises recycling recovered unreacted first or second reagentback to the first or second liquid solutions, respectively, andrecycling recovered first or second solvent back to the first or secondrinsing solutions, respectively.

In certain embodiments, the filtration steps are carried out usingmembrane separation, chemical precipitation, ion-exchange,electrochemical removal, physical adsorption, flow filtrationchromatography, or a combination of these.

In certain embodiments, the first liquid solution comprises more thanone reagent. In some embodiments, the second liquid solution comprisesmore than one reagent. In some embodiments, the first and secondreagents are metalorganic precursors. In other embodiments, the firstand second reagents are cationic or anionic.

In certain embodiments, the first and second liquid solutions furthercomprise an organic solvent, water, or a mixture of both.

In certain embodiments, the thin film comprises a compound selected fromone of the following groups.

-   -   (a) binary oxides of type A_(x)O_(y), where A is an alkali        metal, alkali-earth metal, transition metal, semimetal or        metalloid and x and y are stoichiometric coefficients;    -   (b) ternary oxides of type A_(x)B_(y)O_(z), where A and B are        any combination of alkali metal, alkali-earth metal, transition        metal, semimetal or metalloid and x, y and z are stoichiometric        coefficients;    -   (c) quaternary oxides of type A_(w)B_(x)C_(y)O_(z), where A, B        and C are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid and w, x, y and z are        stoichiometric coefficients;    -   (d) binary halides of type A_(x)B_(y), where A is an alkali        metal, alkali-earth metal, transition metal, semimetal or        metalloid, B is a halogen and x and y are stoichiometric        coefficients;    -   (e) ternary halides of type A_(x)B_(y)C_(z), where A and B are        any combination of alkali metal, alkali-earth metal, transition        metal, semimetal or metalloid, C is a halogen and x, y and z are        stoichiometric coefficients;    -   (f) quaternary halides of type A_(w)B_(x)C_(y)D_(z), where A, B        and C are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid, D is a halogen and w,        x, y and z are stoichiometric coefficients;    -   (g) binary nitrides of type A_(x)N_(y), where A is an alkali        metal, alkali-earth metal, transition metal, semimetal or        metalloid and x and y are stoichiometric coefficients;    -   (h) ternary nitrides of type A_(x)B_(y)N_(z), where A and B are        any combination of alkali metal, alkali-earth metal, transition        metal, semimetal or metalloid and x, y and z are stoichiometric        coefficients;    -   (i) quaternary nitrides of type A_(w)B_(x)C_(y)N_(z), where A, B        and C are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid and w, x, y and z are        stoichiometric coefficients;    -   (j) binary chalcogenides of type A_(x)B_(y), where A is an        alkali metal, alkali-earth metal, transition metal, semimetal or        metalloid, B is a chalcogen and x and y are stoichiometric        coefficients;    -   (k) ternary chalcogenides of type A_(x)B_(y)C_(z), where A and B        are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid, C is a chalcogen and        x, y and z are stoichiometric coefficients;    -   (l) quaternary chalcogenides of type A_(w)B_(x)C_(y)D_(z), where        A, B and C are any combination of alkali metal, alkali-earth        metal, transition metal, semimetal or metalloid, D is a        chalcogen and w, x, y and z are stoichiometric coefficients;    -   (m) binary carbides of type A_(x)C_(y), where A is an alkali        metal, alkali-earth metal, transition metal, semimetal or        metalloid and x and y are stoichiometric coefficients;    -   (n) binary oxyhalides of type A_(x)B_(y)O_(z), where A is an        alkali metal, alkali-earth metal, transition metal, semimetal or        metalloid, B is a halogen and x, y and z are stoichiometric        coefficients;    -   (o) binary arsenides of type A_(x)As_(y), where A is an alkali        metal, alkali-earth metal, transition metal, semimetal or        metalloid and x and y are stoichiometric coefficients,    -   (p) ternary arsenides of type A_(x)B_(y)As_(z), where A and B        are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid and x, y and z are        stoichiometric coefficients;    -   (q) quaternary arsenides of type A_(w)B_(x)C_(y)As_(z), where A,        B and C are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid and w, x, y and z are        stoichiometric coefficients;    -   (r) binary phosphates of type A_(x)(PO₄)_(y), where A is an        alkali metal, alkali-earth metal, transition metal, semimetal or        metalloid and x and y are stoichiometric coefficients;    -   (s) ternary phosphates of type A_(x)B_(y)(PO₄)_(z), where A and        B are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid and x, y and z are        stoichiometric coefficients; and    -   (t) quaternary phosphates of type A_(w)B_(x)C_(y)(PO₄)_(z),        where A, B and C are any combination of alkali metal,        alkali-earth metal, transition metal, semimetal or metalloid and        w, x, y and z are stoichiometric coefficients.

In certain embodiments, the compound generated is Al₂O₃, CdS, or TiN.

In certain embodiments, the battery electrode comprises a substrate. Insome embodiments, the substrate is in the form of a foil, sheet, orfilm. In other embodiments, the substrate is in the form of a wafer orpiece of glass. In some embodiments, the substrate is made up of anorganic material selected from the group consisting of polyimide,polyethylene, polyether ether ketone (PEEK), polyester, or polyethylenenapthalate (PEN). In further embodiments, the substrate is made up of ametal, such as copper, aluminum, or stainless steel.

In certain aspects, the present disclosure relates to a liquid phasedeposition method for coating a thin film onto a surface of a batteryelectrode, comprising.

-   -   (a) providing a battery electrode into a reaction chamber;    -   (b) exposing the battery electrode to a first liquid solution        comprising a first reagent to produce a partially coated battery        electrode having a layer comprising an adsorbed first reagent on        the surface of the battery electrode; and    -   (c) exposing the partially coated battery electrode to a second        liquid solution comprising a second reagent, wherein the at        least second reagent reacts with the first adsorbed reagent of        the partially coated battery electrode to produce a fully coated        battery electrode comprising a monolayer of thin film coated        onto the surface of the fully coated battery electrode, the        monolayer of thin film comprising a compound generated from the        reaction of the second reagent and the absorbed first reagent.

In certain embodiments, the method further comprises rinsing thepartially coated battery electrode with a first rinsing solutioncomprising a first solvent to produce a saturated first layer on thepartially coated battery electrode and a first residual solutioncomprising the first solvent and unreacted first reagent; and rinsingthe fully coated battery electrode with a second rinsing solutioncomprising a second solvent to produce a saturated monolayer of thinfilm on the fully coated battery electrode and a second residualsolution comprising the second solvent and unreacted second reagent.

In certain embodiments, the method further comprises passing the firstresidual solution to a first filtration step to separate unreacted firstreagent from the first solvent; and passing the second residual rinsingsolution to a second filtration step to separate the unreacted secondreagent from the second solvent.

In certain embodiments, the method further comprises recycling recoveredunreacted first or second reagent back to the first or second liquidsolutions, respectively; and recycling recovered first or second solventback to the first or second rinsing solutions, respectively.

In certain aspects, the present disclosure relates to a system forcoating a thin film onto a battery electrode, comprising:

-   -   a conveyance apparatus for conveying the battery electrode to:    -   (a) a first reaction chamber where the battery electrode is        exposed to a first liquid solution comprising at least a first        reagent to produce a layer comprising an adsorbed first reagent        on the battery electrode; and    -   (b) a second reaction chamber where the battery electrode having        a layer comprising an adsorbed first reagent is exposed to a        second liquid solution comprising at least a second reagent,        wherein the at least second reagent reacts with the first        adsorbed reagent to produce the thin film on the surface of the        electrode.

In certain embodiments, the conveyance apparatus comprises a series ofrollers for guiding the electrode to the first and second reactionchambers. In some embodiments, the first and second reaction chambersare in the form of a tank, tray, or bath. In some embodiments, the firstand second reaction chambers include a sensor for determining the amountof first or second liquid solution that is in the respective reactionchamber. In some embodiments, the first and second reaction chamberscomprise a valve for regulating the amount of first or second liquidsolution in their respective reaction chambers, said valve controlled bythe sensor in each reaction chamber.

In certain embodiments, the system further comprises a first rinsingchamber located between the first and second reaction chambers, thefirst rinsing chamber containing a first rinsing solution comprising afirst solvent for rinsing the battery electrode conveyed to the firstrinsing chamber by the conveyance apparatus to thereby produce asaturated first layer on the battery electrode and a first residualsolution comprising the first solvent and unreacted first reagent. Insome embodiments, the system further comprises a first filtrationapparatus for separating the unreacted first reagent from the firstsolvent in the first rinsing solution.

In certain embodiments, the system further comprises a second rinsingchamber located after the second reaction chamber, the second rinsingchamber containing a second rinsing solution comprising a second solventfor rinsing the battery electrode conveyed to the second rinsing chamberby the conveyance apparatus to produce the thin film coated on thesurface of the battery electrode. In some embodiments, the systemfurther comprises a second filtration apparatus for separating theunreacted second reagent from the second solvent in the second rinsingsolution.

In certain embodiments, the first filtration apparatus and the secondfiltration apparatus are selected from one of the following: aseparation membrane, a filtration column, or a chromatographic column, achemical or electrochemical separation tank, an adsorption column, or acombination of these.

In certain embodiments, the compound generated by the reaction of theabsorbed first reagent and the second reagent is selected from one ofthe following.

-   -   (a) binary oxides of type A_(x)O_(y), where A is an alkali        metal, alkali-earth metal, transition metal, semimetal or        metalloid and x and y are stoichiometric coefficients;    -   (b) ternary oxides of type A_(x)B_(y)O_(z), where A and B are        any combination of alkali metal, alkali-earth metal, transition        metal, semimetal or metalloid and x, y and z are stoichiometric        coefficients;    -   (c) quaternary oxides of type A_(w)B_(x)C_(y)O_(z), where A, B        and C are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid and w, x, y and z are        stoichiometric coefficients;    -   (d) binary halides of type A_(x)B_(y), where A is an alkali        metal, alkali-earth metal, transition metal, semimetal or        metalloid, B is a halogen and x and y are stoichiometric        coefficients;    -   (e) ternary halides of type A_(x)B_(y)C_(z), where A and B are        any combination of alkali metal, alkali-earth metal, transition        metal, semimetal or metalloid, C is a halogen and x, y and z are        stoichiometric coefficients;    -   (f) quaternary halides of type A_(w)B_(x)C_(y)D_(z), where A, B        and C are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid, D is a halogen and w,        x, y and z are stoichiometric coefficients;    -   (g) binary nitrides of type A_(x)N_(y), where A is an alkali        metal, alkali-earth metal, transition metal, semimetal or        metalloid and x and y are stoichiometric coefficients;    -   (h) ternary nitrides of type A_(x)B_(y)N_(z), where A and B are        any combination of alkali metal, alkali-earth metal, transition        metal, semimetal or metalloid and x, y and z are stoichiometric        coefficients;    -   (i) quaternary nitrides of type A_(w)B_(x)C_(y)N_(z), where A, B        and C are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid and w, x, y and z are        stoichiometric coefficients;    -   (j) binary chalcogenides of type A_(x)B_(y), where A is an        alkali metal, alkali-earth metal, transition metal, semimetal or        metalloid, B is a chalcogen and x and y are stoichiometric        coefficients;    -   (k) ternary chalcogenides of type A_(x)B_(y)C_(z), where A and B        are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid, C is a chalcogen and        x, y and z are stoichiometric coefficients;    -   (l) quaternary chalcogenides of type A_(w)B_(x)C_(y)D_(z), where        A, B and C are any combination of alkali metal, alkali-earth        metal, transition metal, semimetal or metalloid, D is a        chalcogen and w, x, y and z are stoichiometric coefficients;    -   (m) binary carbides of type A_(x)C_(y), where A is an alkali        metal, alkali-earth metal, transition metal, semimetal or        metalloid and x and y are stoichiometric coefficients;    -   (n) binary oxyhalides of type A_(x)B_(y)O_(z), where A is an        alkali metal, alkali-earth metal, transition metal, semimetal or        metalloid, B is a halogen and x, y and z are stoichiometric        coefficients;    -   (o) binary arsenides of type A_(x)As_(y), where A is an alkali        metal, alkali-earth metal, transition metal, semimetal or        metalloid and x and y is a stoichiometric coefficient;    -   (p) ternary arsenides of type A_(x)B_(y)As_(z), where A and B        are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid and x, y and z are        stoichiometric coefficients;    -   (q) quaternary arsenides of type A_(w)B_(x)C_(y)As_(z), where A,        B and C are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid and w, x, y and z are        stoichiometric coefficients;    -   (r) binary phosphates of type A_(x)(PO₄)_(y), where A is an        alkali metal, alkali-earth metal, transition metal, semimetal or        metalloid and x and y are stoichiometric coefficients;    -   (s) ternary phosphates of type A_(x)B_(y)(PO₄)_(z), where A and        B are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid and x, y and z are        stoichiometric coefficients; and    -   (t) quaternary phosphates of type A_(w)B_(x)C_(y)(PO₄)_(z),        where A, B and C are any combination of alkali metal,        alkali-earth metal, transition metal, semimetal or metalloid and        w, x, y and z are stoichiometric coefficients.

In certain embodiments, the system further comprises a motor. The motoris mechanically linked to different components of the system, forexample, rollers, to provide a means for conveying or driving theelectrode through the system. In some embodiments, the system comprisesa computer. The computer may be operably connected or otherwise incommunication with the motor and/or other devices of the system as ameans for controlling the operation and function of the conveyanceapparatus and/or other system components.

In certain aspects, the present disclosure relates to a batteryelectrode, comprising a porous microstructure coated with a monolayer ofthin film, wherein the thin film has a thickness from 0.5 nm to 100 μm.In some embodiments, the battery electrode of claim 46, wherein thebattery electrode has a thickness of 100 nm to 1,000 μm. In someembodiments, the battery electrode comprises pores ranging in a size of0.1 nm to 100 μm. In some embodiments, the battery electrode has a filmporosity of 1-99%. In some embodiments, the porous microstructure iscomposed of graphite, Si, Sn, a Si-graphite composite, a Sn-graphitecomposite, or lithium metal. In other embodiments, die porousmicrostructure is composed of LiNi_(x)Mn_(y)Co_(z)O₂,LiNi_(x)Co_(y)Al_(z)O₂, LiMn_(x)Ni_(y)O_(z), LiMnO₂, LiFePO₄, LiMnPO₄,LiNiPO₄, LiCoPO₄, LiV₂O₅ sulfur or LiCoO₂ where x, y and z arestoichiometric coefficients.

In certain embodiments, the thin film comprises a compound produced by areaction of a first reagent and a second reagent, wherein the reactionoccurs on a surface of an electrode that is fully or partially submergedin a solution comprising said first and second reagents, whereby saidreaction precipitates the compound onto the surface of the electrode. Insome embodiments, the compound comprises a metal oxide. In otherembodiments, the compound comprises a transition metal dichalcogenide.

In certain embodiments, the battery electrode further comprises asubstrate. In some embodiments, the substrate is in the form of a foil,sheet, or film. In some embodiments, the substrate of the batteryelectrode is made up of an organic material selected from the groupconsisting of polyimide, polyethylene, polyether ether ketone (PEEK),polyester, or polyethylene napthalate (PEN). In other embodiments, thesubstrate is made up of a metal, such as copper, aluminum, or stainlesssteel.

In certain embodiments, the method comprises producing a plurality ofunique thin films. In some embodiments, each thin film of the pluralitycomprises different compounds. In further embodiments, the thin filmsmay be grown on top of one another as a stack on the surface of thebattery electrode.

In certain aspects, the present disclosure relates to a method forcoating a thin film onto a surface of a battery electrode, comprising:

-   -   (a) providing a battery electrode onto a conveyance apparatus.    -   (b) transferring, by the conveyance apparatus, the battery        electrode to a reaction chamber comprising a liquid solution        comprising at least two different reagents, and    -   (c) exposing, by the conveyance apparatus, the battery electrode        to the liquid solution, wherein the at least two different        reagents react to produce a fully coated battery electrode        comprising a monolayer of thin film on the surface of the fully        coated battery electrode, the monolayer of thin film comprising        a compound generated from the reaction of the at least two        different reagents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general flow scheme for an embodiment of the method inaccordance with the disclosure. The method includes rinsing/purge stepsas well as filtration steps.

FIG. 2 is a schematic drawing of one embodiment of a system for coatinga thin film onto the surface of a battery electrode in accordance withthe disclosure.

FIGS. 3A-3B are images magnified to 60 kX of a graphite electrodesurface showing the difference in surface morphology between pristine,uncoated graphite (FIG. 3A) and graphite coated with a method inaccordance with the disclosure (FIG. 3B).

FIG. 4 is a scatter plot showing one-way first cycle loss of coatedversus uncoated electrodes.

FIG. 5 is a t-test graph showing significant difference to 95%confidence in first cycle capacity loss between coated and uncoatedanodes due to presence of the coating.

FIG. 6 is a graph showing the change in differential charge/differentialvoltage (dQ/dV) over voltage for an uncoated graphite anode (600) versusa coated graphite anode (601).

FIG. 7 is an illustration of a battery electrode coated with a thin filmin accordance with the present disclosure on top of a foil substrate.

DETAILED DESCRIPTION

The present disclosure provides liquid-phase deposition methods andsystems for forming coatings of thin films of various types andmorphologies and in various configurations. To date, techniques forforming conformal coatings of thin films (<10 micrometer (μm) thickness)on substrates with a microstructure comprising a high degree ofporosity, tortuosity and/or large number of high aspect ratio features(i.e., “non-planar” microstructure) are either ineffective (“line ofsight” limitation of physical vapor deposition) or are costly andtime-consuming (traditional Atomic Layer Deposition (ALD)). Embodimentsof the present disclosure achieve a cost-effective means for forminguniform, conformal layers on non-planar microstructures. Specifically,the present disclosure focuses on forming uniform, conformal layers onthe surface of non-planar battery electrodes.

The method refers generally to a liquid phase coating process for thedeposition of thin films. These films may be used to coat the surfacesof components of electrochemical devices such as batteries. Inparticular, for batteries, such as lithium ion batteries, applicationsthat may benefit with the coatings described herein may includehigh-voltage cathodes, fast charging, silicon-containing anodes, cheaperelectrolytes, and nanostructured electrodes. Thus, in some embodiments,the thin films may be coated onto an electrode of a battery, such as acathode or anode.

An electrode comprises a porous coating on top of a substrate, such as afoil or a sheet. In some embodiments, the battery electrode comprisesgraphite, Si, Sn, a silicon-graphite composite, a Sn-graphite composite,or lithium metal. In some cases, the battery electrode comprisesLiNi_(x)Mn_(y)Co_(z)O₂, LiNi_(x)Co_(y)Al₂O₂, LiMn_(x)Ni_(y)O_(z),LiMnO₂, LiFePO₄, LiMnPO₄, LiNiPO₄, LiCoPO₄, LiV₂O₅, sulfur or LiCoO₂where x, y and z are stoichiometric coefficients.

In certain embodiments, the substrate may be a continuous substrate,typically in the form of a foil or sheet. A “continuous substrate” asused herein refers to a substrate that possesses an aspect ratio of atleast 10:1 between its two largest dimensions, and is sufficientlyflexible so as to be wound onto itself in the form of a roll. It may bemade up of various materials, including but not limited to metal, suchas copper, aluminum, or stainless steel, or an organic material, such aspolyimide, polyethylene, polyether ether ketone (PEEK), or polyester,polyethylene napthalate (PEN).

An example of an embodiment of a coated battery electrode in accordancewith the present disclosure is shown in FIG. 7. A coated batteryelectrode, 700, comprises electrode constituent particles, 701, that arecoated with a thin film, 702. The thin film, 702, may be between 0.5 nmto 100 μm thick. The electrode constituent particles, 701, are situatedon top of a foil substrate, 703.

In certain aspects, the methods and systems provided herein relate togenerating an artificial SEI layer in batteries that may be moreresistant to dissolution than current SEIs, may have sufficient adhesionto the material or component to be coated with adequate mechanicalstability, may be reasonably electrically resistive to preventelectrolyte breakdown while being conductive of ions (as in the case ofbatteries, for example lithium ions), and may be substantially devoid ofany particle-to-particle internal resistance.

A simple flow scheme for an embodiment of the method in accordance withthe disclosure is shown in FIG. 1. While the embodiment of FIG. 1 isrelated to a method for coating a thin film onto the surface of abattery electrode, this description is only representative of acomponent to be deposited using the methods and systems provided hereinand is not to be construed as being limited in any way.

Referring to FIG. 1, a battery electrode, for example, may be exposed,in 100, to a first liquid solution comprising a first reagent(s) in afirst reaction chamber to produce a layer comprising an adsorbed firstreagent(s) on the surface of the electrode.

The first liquid solution comprises at least a first reagent. The firstreagent may be any compound that is able to react with the material ofthe electrode (i.e., the component to be coated) to form a self-limitinglayer. In certain embodiments, the first reagent is a metalorganiccompound. Examples of such metalorganics include, but are not limitedto, aluminum tri-sec butoxide, titanium ethoxide, niobium ethoxide,trimethyl aluminum, and zirconium tert-butoxide. In another embodiment,the first reagent comprises an aqueous solution comprising an ioniccompound. Examples include, but are not limited to, zinc acetate,cadmium chloride, zinc chloride, zirconium chloride, and zinc sulfate.In some embodiments, the first solution may vary in pH. In someembodiments, the first liquid solution may be a solution including ioniccompounds of both cationic and anionic precursors that react to form asolid film, in this case the film growth is limited by the kinetics ofthe film-forming reaction. In some embodiments, the first liquidsolution may be a solution including both metalorganic and oxidizingprecursors that react to form a solid film; in this case the film growthis limited by the kinetics of the film-forming reaction.

In the embodiments where the first reagent is a metalorganic, the firstliquid solution may also comprise a solvent that is used to dissolve orcomplex the first reagent. Preferred solvents include organic solvents,such as an alcohol, for example, isopropyl alcohol or ethanol, alcoholderivatives such as 2-methoxyethanol, slightly less polar organicsolvents such as pyridine or tetrahydrofuran (THF), or nonpolar organicsolvents such as hexane and toluene.

In one embodiment, the first liquid solution is contained within a firstreaction chamber. The reaction chamber must be a device large enough toaccommodate receiving the electrode and to contain the amount of liquidsolution to be used in the self-limiting layer producing reaction. Suchdevices that may be used as the reaction chamber include, but are notlimited to, tanks, baths, trays, beakers, or the like.

The electrode may be transferred to the first reaction chamber by aconveying apparatus. The conveying apparatus, as described in moredetail below, may be adapted and positioned in such a way as to guide ordirect the electrode into and out of the first chamber.

In certain embodiments, the electrode may be submerged, either fully orpartially, into the first and second liquid solutions of the first andsecond reaction chambers, respectively. In other embodiments, theelectrode may be sprayed with the first and second liquid solutions infirst and second reaction chambers, respectively.

In another embodiment, the electrode may be conveyed underneath a slotdie coater, from which the first liquid solution is continuouslydispensed to generate a two-dimensional liquid film. The speed at whichthe electrode is conveyed and the flow rate of fluid through the diedetermines the thickness of the liquid film. The solvent may then simplyevaporate to create a solid film of the dissolved components, or theliquid film may possess reactants that react to precipitate a thin filmon the surface of the electrode. The resulting solid film may be as thinas one atomic monolayer or as thick as 100 microns. The reaction mayoccur while the solvent is still present or after the solvent hasevaporated. If residual solvent remains until after the end of thecoating process, it may be removed by various techniques, such as adoctor blade, air knife, metering knife or similar. The entire slot diecoating process may then be repeated to generate new films of differentchemical composition or to simply generate thicker coatings of the samechemical composition. In this case, the reaction chambers simplycomprise the area where the slot-die coater is located, and do notnecessarily resemble an enclosed space as is suggested by the term“chamber.”

In another embodiment, the electrode may be conveyed through a tankcontaining a coating solution and a gravure roller. In this embodiment,the gravure roller continuously transfers fluid from the dip tank to theadjacent web due to preferential surface tension (wetting) of the weband the roller by the coating solution. As in slot-die coating, theresult is initially a two-dimensional liquid film on the surface of theelectrode. Particular solution, web and roller compositions, forexample, can influence the surface tension of the fluid on both the weband the roller, thereby influencing the coating efficiency of theprocess. The solvent may then simply evaporate to create a solid film ofthe dissolved components, or the liquid film may possess reactants thatreact to precipitate a thin film on the surface of the electrode. Theresulting solid film may be as thin as one atomic monolayer or as thickas 100 microns. The reaction may occur while the solvent is stillpresent or after the solvent has evaporated. If residual solvent remainsuntil after the end of the coating process, it may be removed by varioustechniques, such as a doctor blade, air knife, metering knife orsimilar. The entire gravure coating process may then be repeated togenerate new films of different chemical composition or to simplygenerate thicker coatings of the same chemical composition.

Multiple sequential, repeated steps of the same process (i.e., slot-dieor gravure coating) can be performed with the same or differentsolutions. Solutions may be separated (as in first solution, secondsolution, etc.) to avoid cross-contamination, for instance, or toprevent homogenous nucleation when a heterogeneous film-forming reactionis preferred.

The electrode is exposed to the first liquid solution for a sufficienttime (a “residence time”) so as to allow the first reagent(s) to adsorbonto the electrode surface and generate a continuous layer (i.e.self-limiting layer). Examples of process variables that may influencethis step include solution and electrode temperature, residence time andreagent concentration.

An advantage of the present methods and systems is that the solventsused vary in specific heat capacity and can also be employed as bothheat transfer and precursor transfer media—yielding faster, moreefficient heating of electrodes. Precursors dissolved into solution arealso much more stable with regards to air ambient exposure as comparedto their pure analogs, yielding improved safety and easier handling.

Optionally, the electrode may undergo a first rinsing/purge step, 102,whereby excess first reagent from step 100 is removed with a solvent.Here, most or all of the non-adsorbed first reagent will be removed fromthe electrode surface before moving the electrode to the next processstep. Key process variables include solvent temperature, electrodetemperature, and residence time. 102 is shown in FIG. 1 as a singlestep, however, in certain embodiments, this step may be repeated or mayhave additional rinsing/purging steps to improve first reagent removal.

The rinsing step leaves exactly one saturated (i.e., purified) firstlayer on the electrode and a residual solution comprising the firstsolvent, unreacted first reagent(s) and other reaction byproducts in thereaction chamber.

As an additional optional step, to recover the solvent used in therinsing step and any unreacted reagent, the residual solution may bepassed to a filtration step, 103. The filtration step separates thesolvent from the unreacted reagent (and any reaction byproduct). Thefiltration step also prevents cross-contamination between chambers andavoids slow contamination of rinse solutions with reagent over thecourse of operation. Continuous filtering of rinse baths can not onlymaintain purity of rinse solvent but can also act as a system formaterials recovery, thereby boosting the materials utilizationefficiency of the process. Any filtration techniques known in the artmay be used. Preferred technologies include, but are not limited to,membrane separation, chemical precipitation, ion-exchange,electrochemical removal, physical adsorption, and flow filtrationchromatography.

The separated solvent may be recycled hack to the rinsing step, 102, forreuse. Likewise, the filtered unreacted first reagent(s) may also berecycled back to 100 for further use in the process (not shown).

A partially coated battery electrode, having a layer (i.e., aself-limiting layer) comprising an adsorbed first reagent may then beexposed, in 104, to a second liquid solution comprising a second reagentin a second reaction chamber.

In some embodiments, the second liquid solution may comprise anoxidizing agent, such as an oxide or chalcogenide source, examples ofwhich include, but are not limited to, water, thioacetamide, and sodiumsulfide. A solvent may also be present, which may comprise of polar ornonpolar organic solvents or may just be water. In other embodiments,the second liquid solution may also contain a nitrogen-containingreagent such as ammonia or hydrazine. In some embodiments, the secondsolution may also vary in pH.

The second reagent is of a different and distinct composition ascompared to the first reagent. The second reagent is selected to be ableto react with the adsorbed first reagent to produce a complete monolayerof thin film compound coated onto the electrode.

In some embodiments, the entire film may be formed by reagents exposedto the electrode from the first liquid solution alone. In this case, thesecond solution may be skipped entirely.

In some embodiments, the compound formed may comprise a metal oxide,such as Al₂O₃ and TiO₂.

In other embodiments, the compound formed may comprise Transition MetalDichalcogenides (TMDs). Typical examples of this class of materialsfollow the general chemical formula MX₂, where M is a transition metalsuch as Mo, W, Ti, etc., and X is either S or Se.

In some embodiments, the compound is composed of any combination of thefollowing polymers: polyethylene oxide (PEO), poly vinyl alcohol (PVA),poly methyl methacrylate (PMMA), poly dimethyl siloxane (PDMS), polyvinyl pyrollidone (PVP). Such polymers, when combined with lithium saltssuch as LiClO₄, LiPF₆ or LiNO₃, among others, can yield a solid polymerelectrolyte thin film.

In some embodiments, the compound may comprise, for example, a sulfideor selenide of Mo, Ti, or W. These materials vary widely in theirelectronic properties, such as bandgap, and thus can be used to createtailored semiconductor heterojunctions that will, for example, blockelectron transfer necessary for degrading reactions in lithium-ionbattery operation. Specifically, such mechanisms can be exploited toblock degrading reactions on both anode and cathode surfaces.

In some embodiments, the compound formed may be selected from the groupconsisting of:

-   -   (a) binary oxides of type A_(x)O_(y), where A is an alkali        metal, alkali-earth metal, transition metal, semimetal or        metalloid and x and y are stoichiometric coefficients;    -   (b) ternary oxides of type A_(x)B_(y)O_(z), where A and B are        any combination of alkali metal, alkali-earth metal, transition        metal, semimetal or metalloid and x, y and z are stoichiometric        coefficients;    -   (c) quaternary oxides of type A_(w)B_(x)C_(y)O_(z), where A, B        and C are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid and w, x, y and z are        stoichiometric coefficients;    -   (d) binary halides of type A_(x)B_(y), where A is an alkali        metal, alkali-earth metal, transition metal, semimetal or        metalloid, B is a halogen and x and y are stoichiometric        coefficients;    -   (e) ternary halides of type A_(x)B_(y)C_(z), where A and B are        any combination of alkali metal, alkali-earth metal, transition        metal, semimetal or metalloid, C is a halogen and x, y and z are        stoichiometric coefficients;    -   (f) quaternary halides of type A_(w)B_(x)C_(y)D_(z), where A, B        and C are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid, D is a halogen and w,        x, y and z are stoichiometric coefficients;    -   (g) binary nitrides of type A_(x)N_(y), where A is an alkali        metal, alkali-earth metal, transition metal, semimetal or        metalloid and x and y are stoichiometric coefficients;    -   (h) ternary nitrides of type A_(x)B_(y)N_(z), where A and B are        any combination of alkali metal, alkali-earth metal, transition        metal, semimetal or metalloid and x, y and z are stoichiometric        coefficients;    -   (i) quaternary nitrides of type A_(w)B_(x)C_(y)N_(z), where A, B        and C are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid and w, x, y and z are        stoichiometric coefficients;    -   (j) binary chalcogenides of type A_(x)B_(y), where A is an        alkali metal, alkali-earth metal, transition metal, semimetal or        metalloid, B is a chalcogen and x and y are stoichiometric        coefficients;    -   (k) ternary chalcogenides of type A_(x)B_(y)C_(z), where A and B        are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid, C is a chalcogen and        x, y and z are stoichiometric coefficients;    -   (l) quaternary chalcogenides of type A_(w)B_(x)C_(y)D_(z), where        A, B and C are any combination of alkali metal, alkali-earth        metal, transition metal, semimetal or metalloid, D is a        chalcogen and w, x, y and z are stoichiometric coefficients;    -   (m) binary carbides of type A_(x)C_(y), where A is an alkali        metal, alkali-earth metal, transition metal, semimetal or        metalloid and x and y are stoichiometric coefficients;    -   (n) binary oxyhalides of type A_(x)B_(y)O_(z), where A is an        alkali metal, alkali-earth metal, transition metal, semimetal or        metalloid, B is a halogen and x, y and z are stoichiometric        coefficients;    -   (o) binary arsenides of type A_(x)As_(y), where A is an alkali        metal, alkali-earth metal, transition metal, semimetal or        metalloid and x and y are stoichiometric coefficients;    -   (p) ternary arsenides of type A_(x)B_(y)As_(z), where A and B        are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid and x, y and z are        stoichiometric coefficients;    -   (q) quaternary arsenides of type A_(w)B_(x)C_(y)As_(z), where A,        B and C are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid and w, x, y and z are        stoichiometric coefficients;    -   (r) binary phosphates of type A_(x)(PO₄)_(y), where A is an        alkali metal, alkali-earth metal, transition metal, semimetal or        metalloid and x and y are stoichiometric coefficients;    -   (s) ternary phosphates of type A_(x)B_(y)(PO₄)_(z), where A and        B are any combination of alkali metal, alkali-earth metal,        transition metal, semimetal or metalloid and x, y and z are        stoichiometric coefficients; and    -   (t) quaternary phosphates of type A_(w)B_(x)C_(y)(PO₄)_(z),        where A, B and C are any combination of alkali metal,        alkali-earth metal, transition metal, semimetal or metalloid and        w, x, y and z are stoichiometric coefficients.

In the case that the reaction is between a non-ionic precursor such as ametalorganic with an oxidizer, as in the hydrolysis oftrimethylaluminum, organic moieties are removed and replaced withmetal-oxygen-metal bonds, until all bonds are fully saturated. In thecase that the reaction is between two ionic solutions, as in thereaction between solutions of Cd²⁺ and S²⁻ ions, the high solubilityproduct constant of the reaction promotes precipitation of an ioniccompound, in this case CdS, with the electrode promoting heterogeneousfilm formation by minimizing surface energy.

Similar to 102, the electrode from 104 is then directed to a secondrinsing/purge step, 106, to remove non-adsorbed/unreacted secondreagent.

In certain embodiments, the thin film may have a thickness of about 0.5nm to 100 μm. For example, the thin film may be a thickness within therange of 0.5 nm-10 nm, 10 nm-50 nm, 50 nm-100 nm, 100 nm-500 nm, 500nm-1 μm, 1 μm-10 μm, 10 μm-50 μm, or 50 μm-100 μm.

In some embodiments, 100 to 106 may be repeated any number of timesuntil a desired thickness of thin film coating is formed onto theelectrode. This scheme is indicated by 108, where the electrode coatedwith the thin film is directed back to step 100 for further processing(forming a loop). In some embodiments, the steps will be repeated butwith different precursors, thereby yielding coatings comprising ofstacks of thin films comprising various compounds.

Additionally, during 102 and 106, the rinse or purge solvent may beeither continuously or periodically filtered so that unreactedreagent(s) can be separated and recovered from solvent. This filteringstep is indicated in steps 103 and 105, respectively. Both precursor andsolvent can then be potentially recycled back into the process. Here,the recycling of the solvent is shown by the return arrows. Thesefiltration steps will save significant material costs over the lifetimeof the apparatus. For every wash and rinse step, a filtration step maybe incorporated into the design. The filtration technique is preferablytuned to the types of reagents used in steps 100 and 104. For instance,an aqueous ionic solution may require the types of filtration columnsused in deionizers to be adequately filtered. However, an organometallicmay be better removed by a tangential flow filtration system thatexcludes by molecular weight, for instance.

A schematic drawing of an embodiment of a system for coating a thin filmonto the surface of an electrode is shown in FIG. 2. In FIG. 2, thereaction chambers are shown as sequential tanks or baths containingreaction solutions; the electrode is conveyed into the reaction chamberswith the assistance of a conveying apparatus. While the embodiment ofFIG. 2 is related to a method for coating a thin film onto the surfaceof a battery electrode, this description is only representative of acomponent to be coated using the methods and systems provided herein andis not to be construed as being limited in any way.

The conveying apparatus of FIG. 2 is particularly suited and adapted insuch a way as to guide or direct the battery electrode into and out ofthe first and second reaction chambers in a sequential manner.

The conveyance apparatus, which is preferably automated, comprises aseries of rollers, such as tensioning rollers, positioned in such amanner as to guide or direct the electrode into and out of the first andsecond reaction chambers. In this way, the system can provide for acontinuous liquid deposition process for coating a thin film onto thesurface of an electrode. The series of rollers, 202 a-i, are driven by aconveying motor (not shown). The rollers, 202 a-i, are operated andoriented in such a way to enable an electrode, 201, to be conveyedthrough the system as discussed in greater detail below. The system,200, also comprises a series of chambers, 205, 207, 215, and 217.

In certain embodiments, the first and second reaction chambers mayinclude a sensor for determining or measuring the volume of first orsecond liquid solution that is in the respective reaction chamber or theconcentration of precursor in each respective reaction chamber.Additionally, the first and second reaction chambers may also comprise aregulating valve that is electronically actuated by the sensor. When thesensor (such as a float switch) determines that the liquid solution istoo low, the valve opens up, allowing more liquid solution from anothersource to flow into the reaction chamber. In some cases, a pump (such asa peristaltic pump) is used to drive the liquid solution into thereaction chamber. When the sensor determines that the liquid solution isat the desired level, the valve closes, preventing excess liquidsolution from flowing into the reaction chamber. In some cases, if thesensor determines that the liquid solution is too high in the reactionchamber, the valve opens up, allowing the excess liquid to flow out ofthe reaction chamber. In the case that the sensor detects precursorconcentration, a valve may expose the tank to a stock solution of highprecursor concentration in the circumstance that the tank precursorsolution is detected to be low, and vice-versa. An example of such asensor is an ion-selective electrode.

In further embodiments, the system comprises a first rinsing chamberlocated between the first and second reaction chambers. The firstrinsing chamber contains the first rinsing solution comprising the firstsolvent for rinsing the electrode conveyed to the first rinsing chamberby the conveyance apparatus to produce a saturated first layer on theelectrode and a first residual solution comprising the first solvent andunreacted first reagent.

Likewise, the system may also comprise a second rinsing chamber locatedafter the second reaction chamber. The second rinsing chamber contains asecond rinsing solution comprising a second solvent for rinsing theelectrode conveyed to the second rinsing chamber by the conveyanceapparatus to produce a thin film coated onto the electrode.

Chamber 205 is a first reaction chamber that contains a first liquidsolution comprising a first reagent and a solvent.

Chamber 207 is a first rinsing chamber located after the first reactionchamber, 205, contains a first rinsing solution comprising a firstsolvent A first filtration apparatus, 209, is connected to the firstrinsing chamber, 207. First filtration apparatus 209 has a residue tube,213, that is connected to the first rinsing chamber, 207, and a permeatecollection tube, 211.

Another chamber, 215, is a second reaction chamber located after thefirst rinsing chamber, 207, and contains a second liquid solutioncomprising a second reagent and a solvent.

Chamber 217 is a second rinsing chamber located after the second rinsingchamber, 215. Second rinsing chamber 217 contains a second rinsingsolution comprising a solvent. A second filtration apparatus, 219, isconnected to the second rinsing chamber, 217. Second filtrationapparatus 219 has a residue tube, 223, that is connected to the secondrinsing chamber, 217, and a permeate collection tube, 221.

System 200 further comprises valves 225 a-d located on each of thechambers. 205, 207, 215, and 217, respectively. The valves, 225 a-d, areconnected to a replenishing source (not shown), which provide, whenneeded, additional first liquid solution, second liquid solution, firstreagent, second reagent, or solvent, as in the case for first and secondchambers 215 and 215, respectively, or more first rinsing solution orsecond rinsing solution, as in the case of first and second rinsingchambers, 207 and 217, respectively. Valves 225 a-d may beelectrically-actuated and opened by the triggering of a sensor (notshown), which is adapted to monitor or measure the volume orconcentration of liquid solution in a chamber. The sensors may be dippedinto the liquid solution of each chamber.

In operation, a first portion of an electrode, 203, is first placed on afirst roller, 202 a, which is part of conveying apparatus 201.Typically, the first portion is attached, such as by glue or tape, to aleader material that is strung through the rest of rollers 202 b-i Inthis way, the leader material can guide the electrode through theconveying apparatus, 201, during the process. The leader material maythen be removed from the electrode once the portion of the electrodethat was placed on roller 202 a is conveyed to roller 202 i or whencoating of the entire electrode is completed. An example of such aleader material may be from a previous roll of electrode. In advance ofthe coating of a specific electrode, the previous roll of electrode emay have had a long trailing length with no active material (just foil).Once the previous roll has been processed, this remnant is left strungon the conveying apparatus, and the active material can be slit andremoved. The remnant will then act as a leader to guide the next roll ofelectrode through the conveying apparatus.

Accordingly, the first portion of the electrode, 203, is conveyed intofirst reaction chamber 205 by movement of second roller 202 b, which isalso located within first reaction chamber 205. First portion ofelectrode 203 is exposed within first reaction chamber 205 to a firstliquid solution to produce a self-limiting layer comprising an adsorbedfirst reagent on the surface of the first portion of the electrode. Thefirst portion of electrode, 203, is left in first reaction chamber 205for a certain residence time in order for the reaction to take place.Once the reaction is substantially completed, the first portion ofelectrode 203 is withdrawn from first reaction chamber 205 by movingupward to third roller 202 c.

While this is occurring, a second portion of electrode 203 is conveyedinto first reaction chamber 205. Conveying apparatus operates in acontinuous manner until the desired amount of electrode is coated withthin film.

Returning back to the first portion of electrode 203, the first portionis then conveyed to a first rinsing chamber, 207 by movement of fourthroller 202 d, which is also located within first rinsing chamber 207.The first rinsing chamber, 207, contains a first rinsing solutioncomprising a first solvent for rinsing the electrode 203 to produce asaturated first layer on the electrode and a first residual solutioncomprising the first solvent and unreacted first reagent.

The system may also comprise a filtration apparatus for separatingunreacted reagent from the solvent in the first and second rinsingsolutions. The filtration apparatus may be any device that can performsuch a separation. Preferably, the filtration apparatus is selected fromone of the following, a membrane, a filtration column, or achromatographic column, a chemical or electrochemical separation tank,or an adsorption column.

When needed, the first rinsing solution is passed to first filtrationapparatus 209 to separate the unreacted first reagent from the firstsolvent. The first filtration apparatus, 209, produces a permeate streamenriched in unreacted first reagent and depleted in first solvent and aresidue stream enriched in first solvent and depleted in unreacted firstreagent compared to the first rinsing solution. The permeate stream iscollected in permeate collection tube 211, which may be recycled or sentback to the first reaction chamber, 205. The residue stream is recycledback to the first rinsing chamber, 207, via residue tubing 213.Filtration apparatus, 209, may operate periodically or continuously.From the first rinsing chamber 207, the first portion of electrode 203is then withdrawn from first rinsing chamber 207 by moving upward tofifth roller 202 e.

First portion of electrode 203 is then conveyed into second reactionchamber 215, by moving downward to sixth roller 202 f, which is alsolocated within second reaction chamber 215. Second reaction chamber 215comprises a second liquid solution comprising at least a second reagent.Within second reaction chamber 215, the electrode, 203, is exposed tothe second liquid solution, which reacts with the first adsorbed reagentto produce a monolayer of thin film coated onto the surface of theelectrode. After the reaction is substantially completed, the firstportion of electrode 203 is then withdrawn from second reaction chamber215 by moving upward to seventh roller 202 g.

Next, first portion of electrode 203 is conveyed to a second rinsingchamber, 217, by moving downward to eighth roller 202 h, which is alsolocated within second rinsing chamber 217. The second rinsing chamber,217, contains a second rinsing solution comprising a second solvent forrinsing the electrode to produce a purified monolayer of thin filmcoated onto the surface of the electrode, 203, and a second residualsolution comprising the second solvent and unreacted second reagent.

Similar to the first rinsing solution, the second rinsing solution maybe sent to a second filtration apparatus, 219. Second filtrationapparatus 219 produces a permeate stream enriched in unreacted secondreagent and depleted in second solvent and a residue stream enriched insecond solvent and depleted in unreacted second reagent compared to thesecond rinsing solution. The permeate stream is collected in permeatecollection tube 221, which may be recycled or sent back to the secondreaction chamber, 215. The residue stream is recycled back to the secondrinsing chamber. 217, via residue tubing 223. Filtration apparatus, 219,may operate periodically or continuously.

Finally, first portion of electrode 203 is withdrawn from second rinsingchamber 217 being conveyed up to ninth roller 202 i. From here, thefirst portion may be collected or rolled up until the rest of thedesired portions of the electrode are coated with a thin film.

A similar embodiment of the present disclosure to that described in FIG.2 can involve replacement of bath-deposition reaction chambers 205 and215 with slot-die or gravure coating reaction chambers (not shown). Insuch an embodiment, rinse chambers 207 and 217 may or may not bepresent, depending on the need for a rinse step. In such an embodimentor even in the embodiment described in FIG. 2, an excess solutionremoval technique such as an air knife, doctor blade, metering knife orsimilar can be employed in lieu of a rinse step. In another similarembodiment, 215 may be entirely absent, as the entire depositionreaction may be performed in 205. As such, the apparatus of the presentdisclosure, both in terms of deposition equipment and conveyingequipment, can be considered to be modular and assembled in any specificmanner so as to facilitate a specific solution-deposition process.

Methods of the present disclosure can be implemented using, or with theaid of, computer systems. The computer system can be involved in manydifferent aspects of the operation the present methods, including butnot limited to, the regulation of various aspects of the conveyanceapparatus, such as by directing movement of the conveyance apparatus bymoving the component to be coated into and out of the reaction chambers;by controlling the timing of the opening and closing of valves;detecting the volume of liquid via sensor readings, directing the flowof liquids, such as reagents and buffers, into the reaction chambers;and regulating pumps. In some aspects, the computer system isimplemented to automate the methods and systems disclosed herein.

The computer system may include a central processing unit (CPU, also“processor” and “computer processor” herein), which can be a single coreor multi core processor, or a plurality of processors for parallelprocessing. The computer system may also include memory or memorylocation (e.g., random-access memory, read-only memory, flash memory),electronic storage unit (e.g., hard disk), communication interface(e.g., network adapter) for communicating with one or more othersystems, and peripheral devices, such as cache, other memory, datastorage and/or electronic display adapters. The memory, storage unit,interface and peripheral devices are in communication with the CPUthrough a communication bus (solid lines), such as a motherboard. Thestorage unit can be a data storage unit (or data repository) for storingdata. The computer system can be operatively coupled to a computernetwork (“network”) with the aid of the communication interface. Thenetwork can be the Internet, an internet and/or extranet, or an intranetand/or extranet that is in communication with the Internet. The networkin some cases is a telecommunication and/or data network. The networkcan include one or more computer servers, which can enable distributedcomputing, such as cloud computing. The network, in some cases with theaid of the computer system, can implement a peer-to-peer network, whichmay enable devices coupled to the computer system to behave as a clientor a server.

The CPU can execute a sequence of machine-readable instructions, whichcan be embodied in a program or software. The instructions may be storedin a memory location, such as the memory. Examples of operationsperformed by the CPU can include fetch, decode, execute, and writeback.

The storage unit can store files, such as drivers, libraries and savedprograms.

The storage unit can store programs generated by users and recordedsessions, as well as output(s) associated with the programs. The storageunit can store user data, e.g., user preferences and user programs. Thecomputer system in some cases can include one or more additional datastorage units that are external to the computer system, such as locatedon a remote server that is in communication with the computer systemthrough an intranet or the Internet.

The computer system can communicate with one or more remote computersystems through the network. For instance, the computer system 401 cancommunicate with a remote computer system of a user (e.g., operator).Examples of remote computer systems include personal computers (e.g.,portable PC), slate or tablet PC's (e.g., Apple® iPad, Samsung® GalaxyTab), telephones, Smart phones (e.g., Apple® iPhone, Android-enableddevice, Blackberry®), or personal digital assistants. The user canaccess the computer system via the network.

Methods as described herein can be implemented by way of machine (e.g.,computer processor) executable code stored on an electronic storagelocation of the computer system, such as, for example, on the memory orelectronic storage unit. The machine executable or machine readable codecan be provided in the form of software. During use, the code can beexecuted by the processor. In some cases, the code can be retrieved fromthe storage unit and stored on the memory for ready access by theprocessor 405. In some situations, the electronic storage unit can beprecluded, and machine-executable instructions are stored on memory.

The code can be pre-compiled and configured for use with a machine havea processer adapted to execute the code, or can be compiled duringruntime. The code can be supplied in a programming language that can beselected to enable the code to execute in a precompiled or as-compiledfashion.

Aspects of the systems and methods provided herein, such as the computersystem, can be embodied in programming. Various aspects of thetechnology may be thought of as “products” or “articles of manufacture”typically in the form of machine (or processor) executable code and/orassociated data that is carried on or embodied in a type of machinereadable medium. Machine-executable code can be stored on an electronicstorage unit, such memory (e.g., read-only memory, random-access memory,flash memory) or a hard disk. “Storage” type media can include any orall of the tangible memory of the computers, processors or the like, orassociated modules thereof, such as various semiconductor memories, tapedrives, disk drives and the like, which may provide non-transitorystorage at any time for the software programming. All or portions of thesoftware may at times be communicated through the Internet or variousother telecommunication networks. Such communications, for example, mayenable loading of the software from one computer or processor intoanother, for example, from a management server or host computer into thecomputer platform of an application server. Thus, another type of mediathat may bear the software elements includes optical, electrical andelectromagnetic waves, such as used across physical interfaces betweenlocal devices, through wired and optical landline networks and overvarious air-links. The physical elements that carry such waves, such aswired or wireless links, optical links or the like, also may beconsidered as media bearing the software. As used herein, unlessrestricted to non-transitory, tangible “storage” media, terms such ascomputer or machine “readable medium” refer to any medium thatparticipates in providing instructions to a processor for execution.Hence, a machine readable medium, such as computer-executable code, maytake many forms, including but not limited to, a tangible storagemedium, a carrier wave medium or physical transmission medium.Non-volatile storage media include, for example, optical or magneticdisks, such as any of the storage devices in any computer(s) or thelike, such as may be used to implement the databases, etc. shown in thedrawings. Volatile storage media include dynamic memory, such as mainmemory of such a computer platform. Tangible transmission media includecoaxial cables; copper wire and fiber optics, including the wires thatcomprise a bus within a computer system. Carrier-wave transmission mediamay take the form of electric or electromagnetic signals, or acoustic orlight waves such as those generated during radio frequency (RF) andinfrared (IR) data communications. Common forms of computer-readablemedia therefore include for example: a floppy disk, a flexible disk,hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD orDVD-ROM, any other optical medium, punch cards paper tape, any otherphysical storage medium with patterns of holes, a RAM, a ROM, a PROM andEPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wavetransporting data or instructions, cables or links transporting such acarrier wave, or any other medium from which a computer may readprogramming code and/or data. Many of these forms of computer readablemedia may be involved in carrying one or more sequences of one or moreinstructions to a processor for execution.

The computer system can include or be in communication with anelectronic display that comprises a user interface (UI) for providing,for example, one or more results of sample analysis. Examples of UFsinclude, without limitation, a graphical user interface (GUI) andweb-based user interface.

The methods and systems provided above are now further described by thefollowing examples, which are intended to be illustrative, but are notintended to limit the scope or underlying principles in any way.

EXAMPLES Example 1: Deposition of TiO₂

Titanium isopropoxide is first dissolved in an appropriate anhydroussolvent, such as dry isopropyl alcohol, is adsorbed onto electrodesurface. The component to be coated (such as an electrode) is thencleansed of excess, non-adsorbed titanium isopropoxide using a rinsesolvent. Next, the electrode is introduced to a solution of an oxidizer,such as water, dissolved in an appropriate solvent, such as isopropylalcohol. Hydrolysis results in loss of alkoxide ligand to 2-propanol,leaving an adsorbed moiety with added hydroxyl. In a fourth step, excesssolution of water and solvent is removed by a rinse solvent. A singlemonolayer of titanium oxide is produced. The process may be repeated toyield increasing thickness.

Example 2: Deposition of CdS

Cadmium sulfate (CdSO₄) is first dissolved in an aqueous solution,yielding Cd²⁺ ions adsorbed onto a surface of an electrode. Theelectrode is cleansed of excess, non-adsorbed Cd²⁺. The electrode isthen introduced to an aqueous solution containing an anionic sulfurprecursor, such as thiourea or Na₂S. The pH of the precursor solutionsmay be varied to control rate of reaction. The high solubility productconstant of CdS in this reaction results in the precipitation of asingle monolayer of CdS on the electrode surface, where surface energyminimization promotes nucleation.

Example 3: Deposition of TiN

An electrode (or other component to be coated) is submerged or exposedto a solution of titanium ethoxide dissolved anhydrous ethanol. Theelectrode is cleansed of excess precursor. The electrode is exposed to asolution containing a nitrogen precursor, such as ammonia in pyridine orhydrazine in THF. Reaction of precursor with adsorbed titanium ethoxideresults in a single monolayer of TiN.

Example 4: Coating Thin Films on Graphite Anodes

Coating processes were performed on graphite anodes. Scanning electronmicroscopy with energy dispersive X-ray spectroscopy (SEM-EDX) wasemployed to prove the presence of coating. SEM images showed a distinctchange in the morphology of the surface of graphite anodes from beforeto after coating (FIGS. 3A-3B). EDX measurement of the local Al and Osignals then confirmed that the coating material was in fact, Al₂O₃. Themeasurement of ˜0.9 atomic % Al via EDX is in the range of EDX signalsof Al observed in ˜1 nm ALD-coated graphite anodes demonstrated inliterature. As such, the solution coated Al₂O₃ can be concluded to bewithin the range of coating thicknesses deposited via ALD in literature.

Example 5: Generating Graphite-Li Half-Cells

Coated graphite anodes were paired with Li foils to generate graphite-Lihalf-cells. Half-cells are ideal for generating precise data regardingthe irreversible capacity loss to form SET on graphite. Rapid cycles oflearning were also achievable given that only one charge-discharge cyclewas necessary to measure first cycle capacity loss. As can be seen fromFIGS. 4-5 and Table 1, a statistically significant (to 95% confidence)difference of 1.37% in mean first cycle loss was achieved when comparingAl₂O₃-coated anodes to control.

TABLE 1 Means and Std Deviations Std Num- Std Err Lower Upper Level berMean Dev Mean 95% 95% coated  4 0.084 0.002 0.001 0.081 0.087 uncoated17 0.098 0.008 0.002 0.093 0.102 t-Test uncoated-coated (assumingunequal variances) Difference 0.014 t ratio 6.282 Std Err Diff 0.002 DF18.515 Upper CL Dif 0.018 Prob > |t| <0.0001 Lower CL Dif 0.01 Prob > t <0.0001 Confidence 0.95 Prob < t  1

By plotting the differential charge/differential voltage (dQ/dV) vshalf-cell voltage, it is possible to identify exactly the amount ofcharge transferred during the typical SE formation voltages near0.6-0.8V. As can be seen from FIG. 6, the differential charge from SEgeneration is lower for coated half-cells (601) as opposed to uncoated(600), which is a clear indication that the SEI generation wassuppressed by the coating.

It should be understood from the foregoing that, while particularimplementations have been illustrated and described, variousmodifications can be made thereto and are contemplated herein. It isalso not intended that the present disclosure be limited by the specificexamples provided within the specification. While certain embodimentshave been described with reference to the aforementioned specification,the descriptions and illustrations of the preferable embodiments hereinare not meant to be construed in a limiting sense. Furthermore, it shallbe understood that all aspects of the present disclosure are not limitedto the specific depictions, configurations or relative proportions setforth herein which depend upon a variety of conditions and variables.Various modifications in form and detail of the embodiments will beapparent to a person skilled in the art. It is therefore contemplatedthat the present disclosure shall also cover any such modifications,variations and equivalents.

The invention claimed is:
 1. A method, comprising: exposing a batteryelectrode comprising electrode constituent particles to one or moreliquid solutions to produce an artificial solid electrolyte interphase(SEI) layer coated onto the electrode constituent particles, wherein theartificial SEI layer is substantially devoid of particle-to-particleinternal resistance with respect to the electrode constituent particles.2. The method of claim 1, wherein the artificial SEI layer is formedfrom a reaction between at least two different reagents included in theone or more liquid solutions.
 3. The method of claim 1, comprising:exposing the electrode constituent particles of the battery electrode toadditional amounts of the one or more liquid solutions one or moreadditional times to generate one or more additional artificial SEIlayers coated onto the artificial SEI layer to produce multiple stackedlayers of artificial SEI layers.
 4. The method of claim 1, wherein thebattery electrode is a lithium-ion battery electrode.
 5. The method ofclaim 1, wherein the battery electrode is an anode or a cathode.
 6. Themethod of claim 1, wherein the electrode constituent particles withinthe battery electrode are deposited on a substrate.
 7. The method ofclaim 6 wherein the electrode constituent particles are composed ofgraphite, Si, fin, a Si-graphite composite, a Sn-graphite composite,lithium metal, LiNi_(x)Mn_(y)Co_(z)O₂, LiNi_(x)Co_(y)Al_(z)O₂,LiMn_(x)Ni_(y)O_(z), LiMnO₂, LiFePO₄, LiMnPO₄, LiNiPO₄, LiCoPO₄, LiV₂O₅,sulfur or LiCoO₂, where x, y and z are stoichiometric coefficients. 8.The method of claim 6, wherein the substrate is a foil, sheet, or film.9. The method of claim 6, wherein the substrate is comprised of anorganic material selected from the group consisting of polyimide,polyethylene, polyether ether ketone (PEEK), polyester, and polyethylenenapthalate (PEN).
 10. The method of claim 6, wherein the substrateincludes a metal.
 11. The method of claim 10, wherein the metal includescopper, aluminum, or stainless steel.
 12. The method of claim 1, whereinthe electrode constituent particles of the battery electrode are exposedto the one or more liquid solutions by spraying, slot die coating, bathcoating, or gravure roller coating.
 13. The method of claim 1, whereinthe battery electrode comprising the electrode constituent particles isexposed to the one or more liquid solutions by an automated conveyanceapparatus.
 14. The method of claim 13, wherein the automated conveyanceapparatus comprises a series of rollers.
 15. The method of claim 1,further comprising rinsing the artificial SEI layer with one or morerinsing solutions comprising at least one solvent to produce one or moreresidual solutions.
 16. The method of claim 15, further comprisingfiltering the one or more residual solutions, each residual solutioncomprising the at least one solvent and unreacted reagent, therebyseparating the unreacted reagent from the solvent to produce recoveredunreacted reagent.
 17. The method of claim 16, further comprisingrecycling the recovered unreacted reagent such that additional amountsof the one or more liquid solutions include the recovered unreactedreagent.
 18. The method of claim 2, wherein at least one of the at leasttwo different reagents includes a metalorganic precursor.
 19. The methodof claim 2, wherein at least one of the at least two different reagentsis cationic, anionic, or non-ionic.
 20. The method of claim 1, whereinthe one or more liquid solutions further comprise an organic solvent,water, or a mixture of both.
 21. The method of claim 1, wherein theartificial SEI layer comprises a compound selected from one of thefollowing groups: (a) binary oxides of type A_(x)O_(y), where A is analkali metal, alkali-earth metal, transition metal, semimetal ormetalloid and x and y are stoichiometric coefficients; (b) ternaryoxides of type A_(x)B_(y)O_(z), where A and B are any combination ofalkali metal, alkali-earth metal, transition metal, semimetal ormetalloid and x, y and z are stoichiometric coefficients; (c) quaternaryoxides of type A_(w)B_(x)C_(y)O_(z), where A, B and C are anycombination of alkali metal, alkali-earth metal, transition metal,semimetal or metalloid and w, x, y and z are stoichiometriccoefficients; (d) binary halides of type A_(x)B_(y), where A is analkali metal, alkali-earth metal, transition metal, semimetal ormetalloid, B is a halogen and x and y are stoichiometric coefficients;(e) ternary halides of type A_(x)B_(y)C_(z), where A and B are anycombination of alkali metal, alkali-earth metal, transition metal,semimetal or metalloid, C is a halogen and x, y and z are stoichiometriccoefficients; (f) quaternary halides of type A_(w)B_(x)C_(y)D_(z), whereA, B and C are any combination of alkali metal, alkali-earth metal,transition metal, semimetal or metalloid, D is a halogen and w, x, y andz are stoichiometric coefficients; (g) binary nitrides of typeA_(x)N_(y), where A is an alkali metal, alkali-earth metal, transitionmetal; semimetal or metalloid and x and y are stoichiometriccoefficients; (h) ternary nitrides of type A_(x)B_(y)N_(z), where A andB are any combination of alkali metal, alkali-earth metal, transitionmetal, semimetal or metalloid and x, y and z are stoichiometriccoefficients; (i) quaternary nitrides of type A_(w)B_(x)C_(y)N_(z),where A, B and C are any combination of alkali metal, alkali-earthmetal, transition metal, semimetal or metalloid and w, x, y and z arestoichiometric coefficients; (j) binary chalcogenides of typeA_(x)B_(y), where A is an alkali metal, alkali-earth metal, transitionmetal, semimetal or metalloid, B is a chalcogen and x and y arestoichiometric coefficients; (k) ternary chalcogenides of typeA_(x)B_(y)C_(z), where A and B are any combination of alkali metal,alkali-earth metal, transition metal, semimetal or metalloid, C is achalcogen and x, y and z are stoichiometric coefficients; (l) quaternarychalcogenides of type A_(w)B_(x)C_(y)D_(z), where A, B and C are anycombination of alkali metal, alkali-earth metal, transition metal,semimetal or metalloid, D is a chalcogen and w, x, y and z arestoichiometric coefficients; (m) binary carbides of type A_(x)C_(y),where A is an alkali metal, alkali-earth metal; transition metal,semimetal or metalloid and x and y are stoichiometric coefficients; (n)binary oxyhalides of type A_(x)B_(y)O_(z), where A is an alkali metal,alkali-earth metal, transition metal, semimetal or metalloid, B is ahalogen and x, y and z are stoichiometric coefficients; (o) binaryarsenides of type A_(x)As_(y), where A is an alkali metal, alkali-earthmetal, transition metal, semimetal or metalloid and x and y arestoichiometric coefficients; (p) ternary arsenides of typeA_(x)B_(y)As_(z), where A and B are any combination of alkali metal,alkali-earth metal, transition metal, semimetal or metalloid and x, yand z are stoichiometric coefficients; (q) quaternary arsenides of typeA_(w)B_(x)C_(y)As_(z), where A, B and C are any combination of alkalimetal, alkali-earth metal, transition metal, semimetal or metalloid andw, x, y and z are stoichiometric coefficients; (r) binary phosphates oftype A_(x)(PO₄)_(y), where A is an alkali metal, alkali-earth metal,transition metal, semimetal or metalloid and x and y are stoichiometriccoefficients; (s) ternary phosphates of type A_(x)B_(y)(PO₄)_(z) where Aand B are any combination of alkali metal, alkali-earth metal,transition metal, semimetal or metalloid and x, y and z arestoichiometric coefficients; and (t) quaternary phosphates of typeA_(w)B_(x)C_(y)(PO₄)_(z), where A, B and C are any combination of alkalimetal, alkali-earth metal, transition metal, semimetal or metalloid andw, x, y and z are stoichiometric coefficients.
 22. The method of claim1, wherein the artificial SET layer comprises a compound comprising anycombination of the following polymers: polyethylene oxide (PEO), polyvinyl alcohol (PVA), poly methyl methacrylate (PMMA), poly dimethylsiloxane (PDMS), and poly vinyl pyrollidone (PVP).